Apparatus for slaking lime



July 10, 1951 R. s. WALKER- APPARATUS FOR SLAKING LIME Original Fil edFeb. 20, 1946 mm B B @m 5 mm 5 m 8 E 5 om w 0F 0 N0 3 mm g mm 3 7 8. .Emm 8 1m E Inventor Robcrf 5. Walker W @015 )W Patented July 10, 1951APPARATUS FOR SLAKI NG LIME Robert S. Walker, Allentown, Pa., a'ssignorto Traylor Engineering & Manufacturing Company, Allentown, Pa acorporation of Delaware Original application February 20, 1946, SerialNo. 649,056. Divided and this application June 4, 1948, Serial No.31,120

4 Claims.

This invention relates to means for producing milk of lime, an objectbeing to produce a milk wherein the particles have the desired physicalcharacteristics as to size and shape, particularly the latter. To thisend the invention contemplates separate slaking and diluting steps, thephysical characteristics of the particles being determined in theslaking step by maintaining a selected substantially constant slakingtemperature. In this connection, it is an object of the invention toproduce a milk of lime of desired consistency and particle form byapportioning a total amount of liquid between slaking and dilutingfunctions so that Whatever proportion is supplied in the slakin step,the complement is supplied in thediluting step.

Typical apparatus in accordance with the invention is shown in theaccompanying drawing which is a vertical axial section of a lime slakerand appurtenances with parts in elevation.

In the drawing, reference numeral designates a cylindrical shellsupported substantially horizontally on rings as at 52 and rollers as at53 of conventional design. Embracing the drum and fixed thereto is. aring gear 54 engaged by a gear 55 driven from a motor 56 through a speedreducer 51. At the right or head end the drum is provided with anannular flange 58 defining an opening 59 which is circular on the axisof the drum, the outer margin of the flange bein rimmed by an' outwardlyflaring conical lip 6E3. 'At its foot end the drum includes an outwardlytapering coaxial conical portion 6| defining an end opening 62, and aspiral rib S3 is aiiixed to the inner surface of extension 6|. 7

Mounted concentrically within drum 5| in the head end thereof is aninner cylindrical shell or'drum 64, an annular space 65 existing betweenthe two drums. Reference numeral 66 designates a spiral rib affixed tothe inner surface 'of drum 5| outwardly of drum 64 with the inner edgeof the rib spaced from the latter except that the rib may includespoke-like extensionsfor the support of the inner drum. At its head endthe inner drum has a tapered, conical terminal portion 61 whose outerextremity defines an opening 68 circular on the drum axis and is spacedinwardly of the edge of flange 58 so that an annular space existsbetween the two.

Reference numeral 69 designates a conveyor, here shown as a screwconveyor, in connection with a source of lime, not shown, the conveyordischarging into a spout which extends into the inner drum throughopening 68. The conveyor is driven by a variable speed device, forexample a motor I I.

Reference numeral 12 designates a pipe leading from any suitable source,not shown, of a slaking and diluting liquid, pipe 12 being connectedinto a flow meter 13 whose outlet is-in xGil 2 connection with a pipe Mwhich extends into the head end of the inner drum through opening 68, acontrol valve 15 being interposed in pipe M and the valve being operableby an electric motor l6. Reference numeral ll designates a controlmember responsive to the driving device 'ii and controlling the flowmeter 13 through any suitable connection 18.

Reference numeral 19 designates a thermocouple supported in the head endof the inner drum preferably in a position to be submerged in thereactants, the thermocouple occupyinga fixed position. Wires and 8|connect the thermocouple to a control instrument 82 which has atemperature scale 83 and a manually settable pointer 85, this instrumentcontrolling motor 16 for drive in either direction through a connection85.

The foot end of the outer drum extends into a chamber 88, through asuitable seal, the chamber including a sump 81 which can be opened forischarge. A conduit 88 connects chamber 81 with the inlet of a fancasing 89. The casing has a vertical outlet conduit 90 extendin into thebottom of a chamber 9! in which is disposed a series of conical baffies92 aligned with conduit 9B. A stack 93 surmounts chamber 9|.

Branched from pipe 14 in advance of valve 15 is a pipe as which througha riser portion 95 is in connection with a vertical header 96 into whichare connected pipe sections 91 which extend into chamber 9| and havedownwardly directed delivery openings above baffles 92 respectively. Apipe 98 leads from the bottom of chamber 9| into the foot end of theouter drum. With the drums rotating, as driven from motor 56, conveyerBQis driven so as to deliver a constant quantity of lime into the head endof the inner drum. In order to produce a milk of lime of desiredconsistency a total amount of liquid proportional to the amount of fedlime must be supplied and flow meter i3 is adjusted so that the requiredtotal quantity is delivered to pipe 14. Should the speed of the variablespeed driving device ll be changed, thus varying the output of conveyor69, the setting of the flow meter 13 will be correspondingly changedthrough controller H and connection 18, so that the correct proportionof water to lime will be maintained.

Depending on the desired characteristic of the ultimate particles ofslaked lime, a certain slaking temperature must be maintained. Thistemperature will be somewhat between and 200 F. Due to the variablesencountered, no definite temperatures of general application can bespecified but as soon as the plant is set up, the required temperaturecan be readily determined. In order to produce a particle of granularform, and this will be the form demanded-if the slaker output is to becentrifuged as later described, the slaking temperature may, forexample, be required to be 186 F. In that case, pointer 84 is set atthis figure on the scale 83 and valve '16 will assume an adjustment suchthat sufficient slaking liquid will be supplied to the inner drum tomaintain the set temperature. This may require, for example,approximately one-third of the metered amount of liquid.

In order to obtain the required cooling effect it is always necessary tosupply more slaking liquid than the minimum necessary for the completionof the reaction and, consequently, the resultant, or reaction product,will always be of a viscous putty-like consistency instead of in a drycondition. The resultant, or reaction product moves toward the foot endof the slaking chamber defined by the inner drum under the combinedinfluences of the rotation of the drum 64 and the continued feed of limeand liquid at the head end. The slaking chamber is long enough withrespect to the rate of feed so that the reaction will be completedtherein and the product will break down to the viscous putty-likeconsistency above-mentioned.

This consistency will, of course, vary under different conditions. Forexample, if the slaking liquid is relatively cold, less will be requiredfor cooling than as though it were relatively warm, the quantity of fedlime remaining constant. However, there is always an excess of liquidbeyond the minimum required for the reaction but the excess will be farshort of that required to produce a milk and, hence, the slaked limewill emerge from the foot end of the slaking chamber in the aforesaidviscous or putty-like consistency and will drop into the outer chamberdefined by drum 5|.

Such 'of the metered liquid as is not passed by valve 15 enters pipe 94,and goes to the sprays 91 for'discharge on the baflles 92, thus servingto condense steam pulled by the fan from drum 5| and discharged intochamber 9|. The liquid flows from member 9| through pipe -98 into thefoot end of driun 5| as diluting liquid.

The slaked lime and diluting liquid fiow with mixing action over thespiral rib 66 toward the head end of drum 5|, and a well dispersedproduct overflows through opening 59 and over lip (it into a surge tank99 whence the milk may be lead away through a pipe N30 or may go to acentrifuge NH. 59 is below the lowest point of opening 52 at the footend of the conveyor so that overflow will occur only at the head end.The spiral rib 63 in the foot end of the outer drum serves to conveytailings through opening 82 to the sump 81. The pitch of the spirals 66and 63 is such that the drum is normally rotated in a counterclockwisedirection, looking toward the right-hand or head end thereof. Hence,grit, tailings, and other foreign matter, precipitated from thesuspension flowing toward the right will be positively mechanically fedtoward the left where it will be picked up by the rib 63 and dischargedthrough opening 62, as noted above.

If in normal operation one-third of the metered liquid is required forslaking, it will be evident that two-thirds of the liquid will be usedfor diluting. In view of the head provided by the riser 95 there willalways be preferential delivery through valve '15 so that of the totalquantity of liquid required to produce a milk of lime of the desiredconsistency, the slaking requirement is first satisfied and the balanceis used for dilution. If there The lowest point of opening,

4 is a change in the temperature of the metered liquid, for example, ifit becomes colder, less will be required in the slaking chamber andvalve 16 will operate to reduce the supply appropriately, the

thus increased balance serving for dilution. Likewise, if the output ofconveyor 69 drops, less slaking liquid will be required for themaintenance of the slaking temperature and valve 15 will be closed tothe appropriate extent.

The described apparatus is usable with great advantage as acausticizingsystem. In that case, pipe 72 is in connection with a sourceof green liquor with the slaking and diluting operations following inthe same manner as above described. Where the slaker output is to becentrifuged, as herein particularly contemplated, the slakingtemperature is maintained at a point such that slaked lime and calciumcarbonate particles'of substantially granular form and appropriate sizewill be produced. Granular particles, as opposed to flake particles, areheavier per unit of surface area, will settle readily and, by the sametoken, can be separated out of the white liquor by centrifuging, whereassuch separation is impossible with concentrated white liquor which hasbeen causticized :by prior art methods. With the surge tank 99 inconnection with the centrifuge I01, white liquor will be delivered at 32and the calcium carbonate sludge at H3. The centrifuge may be of anysuitable type, for example, such as is shown in Patent No. 2,085,538, S.C. Lyons, June 29, 1937.

A thoroughly causticized discharge will ordinarily emerge at opening 59.However, if necessary, an auxiliary causticizer I04, which may be simplya paddle mixer, or equivalent device. can be provided. A valved pipe H15leads-from tank 99 to the inlet of the mixer and a pump I06 is inconnection with the outlet for delivery to the centrifuge. The auxiliarycausticizer is by-passed when not needed.

The invention thus provides not only an improved apparatus or system forthe production of milk of lime but, in particular, an improvedcausticizing system. The two-stage procedure with determination of theparticle form in the first stage is the best mamier known to me for thecertain production of the granular particle form essential to successfulcentrifuging of the suspension. However, I do not necessarily limitmyself to this particular procedure in the preparation of acentrifugeable prod-uct. Other variations in procedure and variations inapparatus are contemplated under the invention as defined in thefollowing claims.

This application is a division of my prior filed application, Serial No.649,056, filed February 20, 1946, for Method and and Means for ProducingMilk of Lime and for Producing White Liquor and Lime Carbonate Sludge,and is directed to the apparatus phase of the invention originallyshown,

described and claimed therein.

I claim:

1. Apparatus for slaking lime and producing milk of lime comprisingconcentric inner and outer drums arranged for rotation in unisonon asubstantially horizontal axis, means for feeding unslaked lime at apredetermined constant rate to the head end of the inner drum, means forsupplying slakingliquid at a predetermined, constant rate, proportionalto the fed lime to produce a milk of lime of desired consistency, meansfor delivering a portion of the supplied liquid to-the head end of theinner drum for admixture therein with the total of the fed lime toproduce a slaked lime of viscous consistency, the foot end of the innerdrum being open for the discharge of the material into the outer drum, acombined dust collector and steam condenser in communication with thefoot end of the outer drum, means causing a draft of air, steam, anddust through the drums for discharge into said collector, means forcontinuously spraying the remainder of the fed liquid into saidcollector, means for conducting the sprayed liquid into the foot end ofthe outer drum for admxiture with the slaked lime, to produce a milk oflime of the desired consistency, and means for discharging the milk oflime from the head end of the outer drum.

2. Apparatus in accordance with claim 1 characterized by the inclusionof means for determining the temperature of the material in the innerdrum, and means responsive to said temperature for proportioning thedelivery of the fed quantity of liquid between the head end of the innerdrum and the foot end of the outer drum.

3. Apparatus in accordance with claim 1 characterized by the inclusionof means for determining the temperature of the material in the innerdrum, and means responsive to said temperature for proportioning thedelivery of the fed quantity of liquid between the head end of the innerdrum and said dust collector and steam condenser.

4. An apparatus for slaking lime and producing milk of lime, comprisinginner and outer concentric, open-ended drums journalled for rotation ona common, substantially horizontal axis, means for deliveringunslakedlime at a substantially constant predetermined rate to the head end ofthe inner drum, means for supplying slaking liquid at a constantpredetermined rate to produce a milk of lime oi the desired consistency,means for delivering a portion of the supplied liquid to the head end ofthe inner drum to produce a slaked lime of viscous consistency thereinfor, delivery from the foot end of the inner drum to the interior of theouter drum, a chamber in communication with the open foot end of theouter drum having baffles therein, means for causing a flow of steam anddust from the drums into said chamber, means for spraying the remainderof the supplied liquid into the chamber to condense steam and collectdust, means for conducting the sprayed liquid from said chamber to thefoot end of the outer drum for admixture with the slaked lime for theproduction of milk of lime of the desired consistency, and means forcausing the milk of lime to flow toward the head end of the outer drumfor discharge therethrough.

ROBERT S. WALKER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date Re. 18,510 Green July 5, 19321,018,404 Baxter Feb. 27, 1912 1,917,300 Hardinge July 11, 19331,945,652 Martin Feb. 6, 1934 2,020,098 Bird Nov. 5, 1935 2,041,544Hammond May 19, 1936 2,047,202 Hardinge July 14, 1936 2,149,269 BrooksMar. 7, 1939 2,365,736 Warner Dec. 26, 1944 2,375,499 Shigley May 8,1945

1. APPARATUS FOR SLAKING LIME AND PRODUCING MILK OF LIME COMPRISINGCONCENTRIC INNER AND OUTER DRUMS ARRANGED FOR ROTATION IN UNISON ON ASUBSTANTIALLY HORIZONTAL AXIS, MEANS FOR FEEDING UNSLAKED LIME AT APREDETERMINED CONSTANT RATE TO THE HEAD END OF THE INNER DRUM, MEANS FORSUPPLYING SLAKING LIQUID AT A PREDETERMINED, CONSTANT RATE, PROPORTIONALTO THE FED LIME TO PRODUCE A MILK OF LIME OF DESIRED CONSISTENCY, MEANSFOR DELIVERING A PORTION OF THE SUPPLIED LIQUID TO THE HEAD END OF THEINNER DRUM FOR ADMIXTURE THEREIN WITH THE TOTAL OF THE FED LIME TOPRODUCE A SLAKED LIME OF VISCOUS CONSISTENCY, THE FOOT END OF THE INNERDRUM BEING OPEN FOR THE DISCHARGE OF THE MATERIAL INTO THE OUTER DRUM, ACOMBINED DUST COLLECTOR AND STEAM CONDENSER IN COMMUNICATION WITH THEFOOT END OF THE OUTER DRUM, MEANS CAUSING A DRAFT OF AIR, STEAM, ANDDUST, MEANS THE DRUMS FOR DISCHARGE INTO SAID COLLECTOR, MEANS FORCONTINUOUSLY SPRAYING THE REMAINDER OF THE FED LIQUID INTO SAIDCOLLECTOR, MEANS FOR CONDUCTING THE SPRAYED LIQUID INTO THE FOOT END OFTHE OUTER DRUM FOR ADMIXTURE WITH THE SLAKED LIME, TO PRODUCE A MILK OFLIME OF THE DESIRED CONSISTENCY, AND MEANS FOR DISCHARGING THE MILK OFLIME FROM THE HEAD END OF THE OUTER DRUM.